From: Pavel Hrdina <phrdina@redhat.com>

Function virHostdevNeedsVFIO is used only in QEMU to figure out if the
host device needs access to /dev/vfio/vfio, for PCI host devices that is
true only if libvirt is not using IOMMUFD.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
---
 src/conf/domain_conf.c      | 13 +++++++++++++
 src/conf/domain_conf.h      |  3 +++
 src/hypervisor/virhostdev.c |  2 +-
 src/libvirt_private.syms    |  1 +
 4 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 01e2bd631a..2d6ae64210 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -33079,6 +33079,19 @@ virHostdevIsPCIDeviceWithIOMMUFD(const virDomainHostdevDef *hostdev)
 }
 
 
+/**
+ * virHostdevIsPCIDeviceWithIOMMUFD:
+ * @hostdev: host device to check
+ *
+ * Returns true if @hostdev is a PCI device with IOMMUFD disabled, false otherwise.
+ */
+bool
+virHostdevIsPCIDeviceWithoutIOMMUFD(const virDomainHostdevDef *hostdev)
+{
+    return virHostdevIsPCIDeviceImpl(hostdev, VIR_TRISTATE_BOOL_NO);
+}
+
+
 static void
 virDomainObjGetMessagesIOErrorsSrc(virStorageSource *src,
                                    const char *diskdst,
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index e63230beec..018daef4c7 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -4735,6 +4735,9 @@ virHostdevIsPCIDevice(const virDomainHostdevDef *hostdev)
 bool
 virHostdevIsPCIDeviceWithIOMMUFD(const virDomainHostdevDef *hostdev)
     ATTRIBUTE_NONNULL(1);
+bool
+virHostdevIsPCIDeviceWithoutIOMMUFD(const virDomainHostdevDef *hostdev)
+    ATTRIBUTE_NONNULL(1);
 
 void
 virDomainObjGetMessagesIOErrorsChain(virStorageSource *src,
diff --git a/src/hypervisor/virhostdev.c b/src/hypervisor/virhostdev.c
index 19907c76ba..0d5e582c08 100644
--- a/src/hypervisor/virhostdev.c
+++ b/src/hypervisor/virhostdev.c
@@ -2536,7 +2536,7 @@ virHostdevUpdateActiveNVMeDevices(virHostdevManager *hostdev_mgr,
 bool
 virHostdevNeedsVFIO(const virDomainHostdevDef *hostdev)
 {
-    return virHostdevIsPCIDevice(hostdev) ||
+    return virHostdevIsPCIDeviceWithoutIOMMUFD(hostdev) ||
         virHostdevIsMdevDevice(hostdev);
 }
 
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index cd028c488a..8dbbd7f64d 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -817,6 +817,7 @@ virDomainQemuMonitorEventStateRegisterID;
 virHostdevIsMdevDevice;
 virHostdevIsPCIDevice;
 virHostdevIsPCIDeviceWithIOMMUFD;
+virHostdevIsPCIDeviceWithoutIOMMUFD;
 virHostdevIsSCSIDevice;
 
 
-- 
2.53.0

On Thu, Mar 19, 2026 at 17:36:49 +0100, Pavel Hrdina via Devel wrote:
> From: Pavel Hrdina <phrdina@redhat.com>
> 
> Function virHostdevNeedsVFIO is used only in QEMU to figure out if the
> host device needs access to /dev/vfio/vfio, for PCI host devices that is
> true only if libvirt is not using IOMMUFD.
> 
> Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
> ---
>  src/conf/domain_conf.c      | 13 +++++++++++++
>  src/conf/domain_conf.h      |  3 +++
>  src/hypervisor/virhostdev.c |  2 +-
>  src/libvirt_private.syms    |  1 +
>  4 files changed, 18 insertions(+), 1 deletion(-)

[...]

> diff --git a/src/hypervisor/virhostdev.c b/src/hypervisor/virhostdev.c
> index 19907c76ba..0d5e582c08 100644
> --- a/src/hypervisor/virhostdev.c
> +++ b/src/hypervisor/virhostdev.c
> @@ -2536,7 +2536,7 @@ virHostdevUpdateActiveNVMeDevices(virHostdevManager *hostdev_mgr,

While it seems for now obvious what's happening in the function I'd
suggest adding a comment about why the function, if the device uses
iommufd, returns false here.

>  bool
>  virHostdevNeedsVFIO(const virDomainHostdevDef *hostdev)
>  {
> -    return virHostdevIsPCIDevice(hostdev) ||
> +    return virHostdevIsPCIDeviceWithoutIOMMUFD(hostdev) ||
>          virHostdevIsMdevDevice(hostdev);
>  }

Reviewed-by: Peter Krempa <pkrempa@redhat.com>